java.io.File: accessing files with invalid filename encodings

Question

Because the constructor of java.io.File takes a java.lang.String as argument, there is seemingly no possibility to tell it which filename encoding to expect when accessing the filesystem layer. So when you generally use UTF-8 as filename encoding and there is some filename containing an umlaut encoded as ISO-8859-1, you are basically **. Is this correct?

Update: because noone seemingly gets it, try it yourself: when creating a new file, the environment variable LC_ALL (on Linux) determines the encoding of the filename. It does not matter what you do inside your source code!

If you want to give a correct answer, demonstrate that you can create a file (using regular Java means) with proper ISO-8859-1 encoding while your JVM assumes LC_ALL=en_US.UTF-8. The filename should contain a character like ö, ü, or ä.

BTW: if you put filenames with encoding not appropriate to LC_ALL into maven's resource path, it will just skip it....

Update II.

Fix this: https://github.com/jjYBdx4IL/filenameenc

ie. make the f.exists() statement become true.

Update III.

The solution is to use java.nio.*, in my case you had to replace File.listFiles() with Files.newDirectoryStream(). I have updated the example at github. BTW: maven seems to still use the old java.io API.... mvn clean fails.

Answer 1

The solution is to use the new API and file.encoding. Demonstration:

fge@alustriel:~/tmp/filenameenc$ echo $LC_ALL
en_US.UTF-8
fge@alustriel:~/tmp/filenameenc$ cat Test.java
import java.io.File;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class Test
{

    public static void main(String[] args)
    {
        final String testString = "a/üöä";
        final Path path = Paths.get(testString);
        final File file = new File(testString);
        System.out.println("Files.exists(): " + Files.exists(path));
        System.out.println("File exists: " + file.exists());
    }
}
fge@alustriel:~/tmp/filenameenc$ install -D /dev/null a/üöä 
fge@alustriel:~/tmp/filenameenc$ java Test
Files.exists(): true
File exists: true
fge@alustriel:~/tmp/filenameenc$ java -Dfile.encoding=iso-8859-1 Test
Files.exists(): false
File exists: true
fge@alustriel:~/tmp/filenameenc$ 

One less reason to use File!